"It is a shame that he's not in there right now - he's number six," said the Scot, who apologised in advance of some difficult decisions ahead.
"That just proves the strength of what we have here.
"You've got Luke Donald, Justin Rose, Padraig Harrington, Martin Kaymer and they are not on the world points list.
"And the top four are Lee Westwood, Rory McIlroy, Graeme McDowell and Ian Poulter.
"That is as strong an eight as you can get right there. And only four can play.
"I don't think any captain has had this dilemma before and I, unfortunately, am going to have to leave out some very, very good players, some winners on this year's circuit."
Others who could be left hoping for wild cards are Paul Casey, Sergio Garcia, Henrik Stenson, Robert Karlsson and in-form Welshman Rhys Davies, who Montgomerie suggests is the best putter in Europe.
The battle for places will again be high in the minds of those teeing off in Thursday's first round of the Scottish Open at Loch Lomond and Montgomerie is impressed by the intensity of the competition.
"I've never seen people practice so hard physically, mentally, on every aspect of the game as I've seen this year, especially, and last," said the eight-time European Order of Merit winner and one-time world number two.
McDowell was a winner at Loch Lomond in 2008
"I never worked, ever, as hard as these guys are right now on their games."
McDowell this week returns to competitive action for the first time since his success at Pebble Beach and to a tournament he won in 2008.
The Northern Irishman agreed with Montgomerie that Dubliner Harrington's two Open successes - and his USPGA win in 2008 - had been a motivation.
"Padraig Harrington was a world-class golfer, but 10 years ago he wasn't a world-class ball-striker, said McDowell.
"He always had the short game and mentality to do it. But, when you see a guy work as hard as he has and go win three major championships, it gives everyone belief.
"Because there are guys running around here who think they are more talented than Padraig as far as ball-striking and tee-to-green go and it goes to show what a strong mind and short game can achieve."
Montgomerie believes that McDowell's latest success can only further spur Europeans to success, perhaps at the Scottish Open and the Open itself next week, and the US Open champion agrees.
"Take Rory as an example," added McDowell. "I've never seen a guy so excited about next week.
"I played with him the weekend after I won at Pebble at Royal County Down and he told me he pulled out (of playing Loch Lomond) this week - I inspired him and he wanted to get ready for St Andrews.
"He wants to get ready for next week and now believes he can win majors, quickly."
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